It is generally conceded that large people are generally stronger than small people, although there are notable exceptions. For example, the world record for heavyweight weightlifters is significantly heavier than the world record for middleweight and lightweight weightlifters, even though the smaller lifters may lift more per pound of body weight. An opposite effect is noted where endurance is required, such as in long distance runners. Lighter runners tend to go faster for longer periods of time than stronger but much heavier runners. No one weighing two hundred pounds has ever come close to winning major marathon race, for example.
A fine athlete with excellent conditioning might be able to lift a certain amount of weight with his or her arm or leg, when using specific exercise apparatus. A larger person, very out of shape and not strong for his or her size, will, to the surprise of many, lift much more on the same apparatus. While part of that is due to increased leverage since larger persons tend to have longer arms and legs, that is not the only basis for the increased strength. There is a certain degree of strength which is derived from the work expended by walking around, carrying excess body weight.
We are often amazed at heavy persons, male or female, who dance well and seem "light" on his or her feet. It is truly amazing to know the strength that these people have. These same people struggle to climb two or three flights of stairs when lighter persons are hardly fazed by that same effort.
Recognizing that increased weight leads to increased strength and decreased endurance does not, by itself, suggest any obvious solution for improving conditioning. Taken to one extreme, Sumo wrestlers attempt to gain extreme amounts of weight to achieve great strength. At the same time, they are nearly exhausted at the end of a match which lasts fifteen or thirty seconds. More importantly, it has never been found to be successful as a conditioning exercise for an athletically inclined person to gain weight to achieve strength, followed by losing weight at the time when maximum performance is desired.
Some attempts to carry additional weight have been developed for training exercises. For example, joggers often times carry small weights in their hands and, as a result, achieve some strengthening of the arm muscles. Often times, however, strain in the shoulder, elbow or wrist causes more pain than gain. Weighted belts, wrists bands and leg bands have also placed dangerous strain on joints, particularly when enough weight is used to make a difference. As a result, no effective way to directly increase strength by having greater weight has been developed which does not adversely strain other parts of the body, causing more harm than good. There is no present device available to add a significant amount of body weight without placing potentially harmful strain on a person's joints.